you might have not had enough sugar, and also might not have cooked it long enough. (it's very precise though. so make sure to record your perfect time/temp for future endeavors.)
it's worth trying again though. they're so amazing.
Gosh, that's a good point about the sugar! I looked back at the recipe and it calls for "lightly packed" brown sugar so I think I may have used a little less than I usually do (I usually pack the brown sugar really really firmly and this time I was pretty gentle!). It makes sense since these are sorta candying in the oven that the sugar ratio is important!
ETA: just read the chocolate chip cookies thread and it seems like measuring by volume is so problematic. I know it's cheaper and easier to measure volumetrically but dang it, going by mass seems a lot more consistent